Method of manufacturing a heat exchanger



1.966 D. M. DONALDSON 3,228,367

METHOD OF MANUFACTURING A HEAT EXCHANGER Filed Dec. 20, 1962 2 Sheets-Sheet 1 fiaimarzdfi arzazzzlsvn Jan. 11, 1966 D. M. DONALDSON METHOD OF MANUFACTURING A HEAT EXCHANGER Filed Dec. 20, 1962 2 Sheets-Sheet 2 United States Patent 3,228,367 METHOD OF MANUFACTURING A I-EAT EXCHANGER Desmond M. Donaldson, (lakville, Ontario, Canada, as-

signor to Borg-Warner Corporation, (Ihicago, Ill., a

corporation of Illinois Filed Dec. 20, 1962, Ser. No. 246,070 2 Claims. (Cl. 113-118) This invention relates to heat exchangers and methods of their manufacture, more particularly to a novel method of forming a fin structure from a continuous strip of thin metal stock and the product of such method.

Heat exchangers of the general type to which the present invention pertains comprise a plurality of spaced, fluid conducting tubes arranged generally parallel to one another, supply and receiving headers or tanks interconnected by said tubes, and a plurality of heat exchange promoting fins in heat conducting relation with said tubes. This type of heat exchanger has particular utility used as an automobile radiator; although it should be understood that the present invention is not necessarily limited to this application.

Methods of fabricating fin structure from a continuous strip of metal stock are known in the art. One example is illustrated in R. W. Kritzer, US. Patent No. 2,994,123, issued on August 1, 1961, in which an elongated strip of metal stock is severed along spaced longitudinal lines, provided with a plurality of tube receiving apertures, and then bent in alternate directions between adjacent tube apertures to provide an integral, accordion-pleated structure. Another such example is disclosed in H. E. Schank et al., US. Patent No. 2,252,209, issued August 12, 1941, in which a similar structure is provided by bending a length of metal stock into a pleated pattern and inserting heat exchange tubes between the pleated fins. The heat exchange elements disclosed in Kritzer and Schank et al are designed to receive the major portion of the cooling (or heating) air flow in a direction parallel to the fold lines.

Briefly described, this invention provides a self-stacking heat exchanger fin structure providing a plurality of elongated substantially parallel fin surfaces suitable to receive the major portion of the flow of heat exchange media in a direction across the width dimension of each individual fin element. The fins are preferably formed from a continuous strip of material in a manner such that alternate edges of each fin are tied to the adjacent fin. The tie element provides a means for spacing and aligning the respective fins. Preferably, the tie elements are located inwardly from the edge of the respective fins within the body of the fin assembly and the ties are preferably in staggered or non-aligned positions. The ties are preferably twisted subsequent to insertion of the tubes to provide a means for diverting the flow of air across the fin elements.

Other and more particular objects and advantages will be apparent from the following description taken in conjunction with the appended drawings, wherein:

FIGURE 1 is a front elevation view disclosing a heat exchanger constructed in accordance with the principles of the present invention;

FIGURE 2 is a side elevation view of the heat exchanger illustrated in FIGURE 1;

FIGURE 3 is a partial plan view of a section of metal stock after cutting and stamping but prior to folding and assembly of the tin structure into the completed heat exchange unit;

FIGURE 4 is a view taken along the line 44 of FIGURE 3;

FIGURE 5 is a detailed isometric view illustrating a tie element prior to the step of inserting the tubes;

FIGURE 5A is a detailed isometric view illustrating the tie element in its twisted position subsequent to insertion of the tubes; and

FIGURE 6 is a diagramamtic illustration of the fin structure forming process.

Referring now to FIGURES 1 and 2, the numerals 1 and 2 respectively designate a fluid supply and receiving headers or tanks adapted to to conduct the heat exchange fluid to and from a load device, such as an automobile engine for example. A plurality of fluid conducting tubes 4, having a relatively elongated cross section, and commonly referred to as flat tubes, interconnect the supply header 1 with the receiving header 2. The zone spanned by the tubes is of course a cooling (or heating) zone adapted to receive a current of a fluid heat exchange medium flowing in the direction of the arrows (FIG. 2).

In order to increase the effective area of heat exchange, a plurality of fin elements are provided, said fin elements being in heat conducting relationship with the tubes 4. The fin structure comprises a plurality of superposed, spaced fin sections 6 arranged in generally parallel and generally horizontal relationship, each fin section being interconnected at alternate ends to an adjacent fin section by integral ties 8. The ties preferably have a relatively narrow span with respect to the over-all length of the units to reduce the flow resistance of these elements. It is particularly important that these tie elements are stra tegically positioned in non-aligned positions in successive layers of fins. This enhances the efiiciency of the heat exchanger and minimizes the effect of the tie elements in restricting the flow of air across the fin.

Each fin section is provided with a plurality of tube receiving apertures 10 in superposed relationship with one another, each said receiving aperture being surrounded by a flange 12, projecting from the plane of the fin sections, to facilitate connection to the fluid conducting tubes 4 by soldering, brazing, or some other suitable method.

Having described the over-all construction of the heat exchanger unit as contemplated by the present invention, reference is now made to FIGURES 3, 4, and 6. As best illustrated in FIGURE 3, a partial plan view of a section of sheet metal stock prior to bending into the configuration shown in FIGURE 1, the sheet metal stock, preferably of copper, aluminum or some other metal having a high coeflicient of thermal conductivity and preferably not more than one-hundredth of an inch in thickness, is subjected to a series of mechanical operations which need not be performed in the order described. First of all, the stock is cut to form a plurality of longitudinally spaced groups of slits 14, 15, 16, and 17 each group of slits comprising a series of laterally spaced, co-aligned, individual slits extending transversely across said strip to provide a series of unsevered portions 8 between adjacent individual slits. Next, the stock is provided with a plurality of relatively short, longitudinally extending slits 18 intersecting each individual transverse slit adjacent the terminal portions thereof. The tube apertures 10 are then formed, preferably in a staggered configuration, at locations between adjacent groups of transverse slits. In addition, it has been found to be useful to form the tube engaging flanges 12 in adjacent sections so that they extend in opposite directions, alternating throughout the length of the strip. (FIG. 4.) In so doing, it is apparent from an inspection of FIGURE 4 that this provides a unit in which all of the flanges extend either upwardly or downwardly from the plane of the fin sections after the strip is folded into the completed configuration as shown in FIGURE 1.

FIGURE 6 illustrates in diagrammatic form a practical manufacturing process for the production of the fin structure previously described. From a storage roll 20, the

relatively thin sheet material is delivered by any known intermittent feed device to a pair of cutting mechanisms 21 and 22. These may either be running knife blades or a transversely directed blade which strikes downwardly on the strip of sheet material. Cutting means 21 is adapted to form the first of a series of transversely spaced slits; and the second cutting mechanism 22 form-s a spaced series of slits which are staggered with respect to the first series, as shown in FIGURE 3. This arrangement results in having the ties 8 staggered with respect to each other to minimize excessive air flow resistance due to the span of these ties and balance the heat load across the entire surface of the heat exchanger with respect to each individual tube. From the cutting mechanisms the strip is delivered to a die press 24 which simultaneously forms the tube receiving apertures 10 in a pair of adjacent fin sections. In order to accomplish this result, one-half of the die forms the strip with flanges extending in one direction and the other half of the die forms the apertures With flanges extending in the opposite direction. The strip, now in the form illustrated in FIGURE 3, is delivered to a shaping die 26 having mating sections 26a, 261) which corrugate the strip in the form shown between the shaping die and the condensing rollers 28. The condensing rollers engage the opposite edges of the strip to gather each section and bring adjacent fin sections into parallel alignment with all of the tube apertures coaxially aligned with respect to one another.

The fin stock, in its gathered form, is placed in a jig to support the stock during the tube pushing operation. The tubes are pushed through the aligned tube aperatures in the conventional manner. Subsequent to insertion of the tube members in the fin stock, the tie elements are preferably twisted (FIGURE A) to provide a predetermined flow pattern across the fin stock and minimize the resistance to flow of air across the fin stock.

Manifestly, the construction as shown and described is capable of some additional modification and such modification as may be construed to fall within the scope and meaning of the appended claims is also considered to be within the spirit and intent of the invention.

What is claimed is:

1. A method or manufacturing an integral fin structure having a plurality of spaced parallel fin sections comprising the steps of (1) slitting an elongated strip of relatively thin sheet metal with a plurality of longitudinally spaced groups of transversely extending slits in said strip, each group comprising a series of spaced individual slits extending transversely across the width of said strip, said individual slits being arranged so that there is formed between adjacent slits an uncut portion; (2) forming a plurality of tube apertures at locations between adjacent groups of transverse slits; (3) forming a plurality of relatively shorter longitudinally extending slits intersecting said series of slits adjacent the terminal portions thereof; (4) bending said strip in the vicinity of each aligned group of slits in opposite directions to form a structure in which a plurality of superposed fin sections are joined to an adjacent fin section by the uncut portions defined between the longitudinally extending slits; inserting a plurality of tubes into said fin structure; and (5) twisting each of said tie elements through an angle of about degrees to present an edge portion confronting the normal flow of air through said integral fin structure.

2. A method of manufacturing an intergral fin structure having a plurality of spaced parallel fin sections comprising the steps of (1) slitting an elongated strip of relatively thin sheet metal with a plurality of longitudinally spaced groups of transversely extending slits in said strip, each group comprising a series of spaced individual slits extending transversely across the width of said strip, said individual slits being arranged so that there is formed between adjacent slits an uncut portion; (2) forming a plurality of relatively shorter longitudinally extending slits intersecting said series of slits on an angle substantially perpendicular to said slits adjacent the terminal portions thereof; (3) forming a plurality of tube apertures at locations between adjacent groups of transverse slits; (4) bending said strip in the vicinity of each aligned group of slits in opposite directions to form a structure in which a plurality of superposed fin sections are joined to an adjacent fin section by the uncut portions defined between the longitudinally extending slits; inserting a plurality of tubes into said fin structure; and (5) twisting each of said tie elements through an angle sufficient to present an edge portion of said uncut portion confronting the normal flow of air through said integral fin structure.

References Cited by the Examiner UNITED STATES PATENTS 709,875 9/1902 Commichau 182 1,302,870 5/1919 Spery 15376 2,063,736 12/1936 Hardiman et al. 165-182 2,131,929 10/1935 Amrne 165185 2,426,107 8/1947 Kramer 165-182 2,477,839 8/1949 Vanderweil 165-185 2,644,225 7/1953 Dietz 29157.3 2,716,802 6/1964 Greer 29157.3 2,948,054 5/1961 Kritzer 291S7.3 2,966,781 1/1961 Schae fer et al. 62523 2,994,123 8/1961 Kritzer 113-118 3,100,332 8/1963 Gier 29157.3

FOREIGN PATENTS 506,891 6/1939 Great Britain.

CHARLES W. LANHAM, Primary Examiner.

CHARLES SUKALO, MICHAEL V. BRINDISI,

Examiners. 

1. A METHOD OF MANUFACTURING AN INTEGRAL FIN STRUCTURE HAVING A PLURALITY OF SPACED PARALLEL FIN SECTIONS COMPRISING THE STEPS OF (1) SLITTING AN ELONGATED STRIP OF RELATIVELY THIN SHEET METAL WITH A PLURALITY OF LONGITUDINALLY SPACED GROUPS OF TRANSVERSELY EXTENDING SLITS IN SAID STRIP, EACH GROUP COMPRISING A SERIES OF SPACED INDIVIDUAL SLITS EXTENDING TRANSVERSELY ACROSS THE WIDTH OF SAID STRIP, SAID INDIVIDUAL SLITS BEING ARRANGED SO THAT THERE IS FORMED BETWEEN ADJACENT SLITS AN UNCUT PORTION; (2) FORMING A PLURALITY OF TUBE APERTURES AT LOCATIONS BETWEEN ADJACENT GROUPS OF TRANSVERSE SLITS; (3) FORMING A PLURALITY OF RELATIVELY SHORTER LONGITUDINALLY EXTENDING SLITS INTERSECTING SAID SERIES OF SLITS ADJACENT THE TERMINAL PORTIONS THEREOF; (4) BENDING SAID STRIP IN THE VICINITY OF EACH ALIGNED GROUP OF SLITS IN OPPOSITE DIRECTIONS TO FORM A STRUCTURE IN WHICH A PLURALITY OF SUPERPOSED FIN SECTIONS ARE JOINED TO AN ADJACENT FIN SECTION BY THE UNCUT PORTIONS DEFINED BETWEEN THE LONGITUDINALLY EXTENDING SLITS; INSERTING A PLURALITY OF TUBES INTO SAID FIN STRUCTURE; AND (5) TWISTING EACH OF SAID TIE ELEMENTS THROUGH AN ANGLE OF ABOUT 90 DEGREES TO PRESENT AN EDGE PORTION CONFRONTING THE NORMAL FLOW OF AIR THROUGH SAID INTEGRAL FIN STRUCTURE. 